This pulley is made of fibergrass reinforced polycarbonate. It no longer has an Aluminium Hub with a set screw for attachment. It has a single flange and suits belts up to 9.5mm wide. Overall length is 20.64mm Flange Diameter is 25.1, hub diameter 12.7mm, with a 4.763mm bore to suit our Nema17 stepper motors.